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Ray Nagin has pleaded not guilty to federal bribery and fraud charges.

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Tight rules for public as jury selection starts for ex-New Orleans mayor

Ray Nagin has pleaded not guilty to federal bribery and fraud charges

Prosecutors say he took more than $200,000 in bribes from city contractors

"Corruption is still very hard to prove," lawyer tells CNN

Closed courtrooms. No laptops, phones or Wi-Fi. Bathrooms closed off by marshals.

The corruption trial of former New Orleans Mayor Ray Nagin cranks up Monday with a federal judge imposing tough rules on spectators and reporters during jury selection. In an order issued last week, U.S. District Judge Helen Berrigan imposed those restrictions because of concerns that courtroom rules "may not be respected" by some unnamed miscreants.

Nagin's pleas for federal help for his flooded city caught the nation's attention in the aftermath of Hurricane Katrina in 2005. Now out of office, he's pleaded not guilty to federal charges of bribery, money laundering, fraud and filing false tax returns.

Prosecutors accused him of being at the center of "a bribery and kickback scheme" in which he allegedly received checks, cash, wire transfers, personal services and free travel from businessmen seeking contracts and favorable treatment from the city.

After preliminary questioning, some jurors will be quizzed behind closed doors, Berrigan ordered. Electronic devices have been barred from the courtroom, and the nearby restrooms on the fifth floor of the courthouse "will be closed to all members of the media and public during voir dire proceedings," she wrote.

Those restrictions may be lifted "after the jury is sworn and in the event the court regains confidence that there will be full compliance with its orders by the media and public," she added.

In exchange, businesses that coughed up cash for Nagin and his family won more than $5 million in city contracts, according to an indictment brought in January 2013.

Two businessmen named in the charges have pleaded guilty to making payoffs and are cooperating with prosecutors. A third was found guilty of bribing two Nagin staffers, while another admitted to paying kickbacks to the sheriff of nearby Plaquemines Parish after winning a project management contract there.

But Ashleigh Merchant, a Georgia defense lawyer and legal observer, told CNN, "Corruption is still very hard to prove."

In most businesses, Merchant said, "You're going to give the work to who you know, who you trust, who you perhaps took a family vacation with. The issue is going to be the testimonyof those people, as to whether or not they expected to get something back in return for taking the family on vacation."

And if prosecutors can show that Nagin promised city business in exchange for their favors, "Then he's done," she said.

Nagin sought to have the charges dismissed in October after another federal judge blasted what he called the "grotesque" misconduct of prosecutors in the post-Katrina shootings of unarmed civilians by police at the Danziger Bridge.

The judge tossed out the convictions of five cashiered cops after ruling that members of the U.S. attorney's office tainted their 2011 trial by anonymously posting "egregious and inflammatory" comments at online news sites.

Nagin argued that he was the target of the same underground effort, citing "a continuum of perjorative statements and demeaning racial epithets" aimed at him. The U.S. attorney's office said none of the prosecutors involved in the Danziger Bridge case played a role in the Nagin investigation, and Berrigan denied Nagin's motion.

The onetime cable-television executive was elected mayor in 2002 and was in office when the massive Katrina slammed ashore just east of New Orleans on August 29, 2005. The storm flooded more than three-fourths of the low-lying city and left more than 1,800 dead, most of them in across Louisiana.

Supporters credited Nagin's sometimes-profane demands for aid from Washington with helping reveal the botched federal response to the storm -- a fiasco that embarrassed the George W. Bush administration and led to billions of federal dollars being poured into Gulf Coast reconstruction efforts.

But he also had his critics: A congressional committee criticized him for delaying evacuation orders, and his frantic description of post-storm New Orleans as a violent wasteland with up to 10,000 dead turned out to be greatly exaggerated.

As he sought re-election in 2006, with much of the city's African-American population displaced by storm damage, he was blasted for insisting that New Orleans would remain a "chocolate" city.